Dusty Galaxies in Protoclusters

<p>Comparison of Herschel and Planck sources in large area surveys has revealed a pop- ulation of objects that appear to be galaxy clusters or protoclusters, many of whose members are undergoing massive starbursts. Followup studies confirm the likely clus- ter/protocluster nature of these sources. Similar starbursting sources have also been found through pointed Herschel observations of specific Planck colour-selected sources, and known z > 2 protoclusters. We compare our protocluster candidates to those se- lected in other ways, and to predictions from theoretical models, finding that current cluster formation models do not easily reproduce the protocluster population we see. We also extend our study of dust obscured star formation in dense environments to higher redshifts through studies of known z > 4 protoclusters in Herschel fields.